Leprosy
An age-old disease
that still lingers

Leprosy also known as Hansen’s disease is an age-old disease, that once occurred worldwide. It was spread from East Africa or the Near East along human migration, colonization and trade routes. The oldest skeletal evidence for the disease dates from 2000 BC and were found at the archeological sites of Balathal in India and Harappa in Pakistan. Throughout history, people afflicted have often been ostracized by their communities and families.

 Leprosy is curable and treatment in the early stages can prevent disability.

What causes Leprosy

Leprosy is a bacterial disease that can affect the skin, nerves, eyes and the mucosal lining of the nose. It is caused by a slow-growing bacteria Mycobacterium leprae (more recently, also Mycobacterium Leptomatosis), and can take up to 20 years to show symptoms. The bacteria was first identified by G.H. Armauer Hansen in Norway in 1873 (hence also called Hansen’s diseas), and was also the first bacterium identified as disease-causing in humans.

Scientists currently think leprosy is spread via inhalation of infected droplets released to the air when by coughs/sneezes of infected people. Contrary to what some believe, it cannot be spread by physical contact with infected people, sexually or from mother to unborn babies. In fact for 95% of adults, their immune systems can fight off the disease, and further, treatment is quite effective. However, since symptoms develop very slowly, it is hard to detect the sources. In southern United States, armadillos can be carriers (although the risk is very low).

Photo: M leprae (red)

Where is Leprosy found

Although skeletal evidence suggests its prevalence as early as in 2000 BC in Harappa in modern-day Pakistan, its widespread occurrence across the old and new world in modern history is attributed to migration, colonization and the slave trade routes. In 2019, over two hundred thousand cases were reported, of which 15000 were children (> 40/day) Globally an estimated 2-3 million people are living with leprosy, and the countries with the highest cases in 2019 were India (> 50%), Brazil and Indonesia. Other countries with reported cases include Nepal, Bhutan, Tanzania, Mozambique, Madagascar, western Pacific and the United States. Due to its long incubation period, diagnosis is often delayed and the actually numbers are likely higher.

Image: Leprosy geographical distribution

What are the symptoms of Leprosy

Since leprosy-causing bacteria affect the nerves, these become swollen under the skin, and can cause infected areas to lose sensation which could in turn cause injuries. Affected skin becomes flaky and lighter/darker with a loss of feeling or reddish due to the inflammation of the skin. Painless ulcers on the soles of the feet, painless swelling or lumps in the face and earlobes are some other symptoms.

Early intervention is critical to the treatment of leprosy. If left untreated, the nerve damage associated with leprosy can also lead to blindness, chronic non-healing ulcers in the feet, crippling of the limbs and paralysis. In extreme cases, the body may reabsorb affected digits, loss of eyebrows or show saddle-nose deformity due to damage to the nasal septum.

How can Leprosy be prevented

The current preventive treatment is a single dose of rifampicin in adults and children over 2 years who have been in contact with someone who has leprosy. The bacillus-calmetter-guerrin (BCG) vaccine, which also prevents against tuberculosis, also offers a lower degree of protection against leprosy (26%-41%) in controlled trials.

How is Leprosy diagnosed

The best way to diagnose the disease is a skin or nerve biopsy at a clinic, where healthcare providers look for the bacteria under a microscope. Together with skin lesions and other symptoms consistent with leprosy, the presence of acid-fast (where the bacteria resist de colorization by acids during laboratory staining) bacilli (rod-shaped bacteria) during the biopsy are often considered a positive diagnosis. However, in some cases, the diagnosis is based purely based on symptoms.

Polymerase chain reaction (PCR) tests, such as the ones available from the WoIDMo can detect the M.leprae DNA, although these are combined with the probability of exposure and other symptoms to make the diagnosis.

Photo: skin lesions on the thigh of a person with leprosy

How is Leprosy treated

Leprosy is treated using a combination of 2-3 antibiotics in a multidrug therapy so that the bacteria do not develop antibiotic resistance due to the long duration of treatment (e.g. 1-2 years). It is critical for infected individuals to not stop treatment midway, since the bacteria can re-infect individuals in such cases. Contrary to societal stigma, affected individuals are no longer contagious once treatment starts. The antibiotics used are dapsone with rifampicin, and clofazimine is added for some types of the disease.

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